ik=i+i2+i3+i4+i5+i6+i7+i8+i9+... Now as, i4=i8=i12=...i4n=1 and i+i2+i3+i4=0 ‌‌ So, ‌
n
∑
n=1
ik=i+i2+i3+i4+i5+i6+....i7+i8+i9+... ‌=i+i2+i3+i4+(i+i2+i3+i4)+(i+i2+i3+i4)+... ‌=0+0+0+... When we take n=99 after 96 th term, we will be left with 0+i+i2+i3=−1 So, for ‌‌n=99 ⇒‌‌1+